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| New Integrated Govt. School Physical Science Concern About Our Environment Notes. |
Today we will discuss the first chapter of WBBSE tenth grade physics concern about our environment. Hopefully all the students in the secondary will find it very useful.
Class 10 Physical science concern about our environment
Atmosphere: The invisible gaseous layer that surrounds the earth under the influence of the force of gravity is called the atmosphere.
Although the atmosphere does not have a definite limit, the existence of air can be felt from 750 km to 1000 km above the surface.
- Components of Atmosphere:
The elements that make up the atmosphere are-
1. Gaseous Components: The gaseous components of air include N2 (78.09%), O2 (20.95%). CO2 (0.03%), Ar (0.93%). Helium, neon, methane, xenon, hydrogen, etc. are also found in very small amounts in the air.
2. Water vapor and 3. Dust
- Structure of atmosphere: The arrangement of air layers can be done in two ways -
1) According to the chemical composition and
2) According to the variation of temperature
1) According to the chemical composition:
According to the chemical composition, the atmosphere can be divided into two parts, namely -
a) Homosphere and b) Heterosphere
a) Homosphere: The ratio of different gaseous elements in the atmosphere to an altitude of about 90 km from the earth's surface remains unchanged,i.e. the chemical composition remains the same, so the layer is called homosphere.
b) Heterosphere: This layer is called the heterosphere because the ratio of all the chemical elements in the atmosphere from 90 km to 10000 km above the homosphere is not the same.
2) Depending on the temperature:
The atmosphere is divided into roughly six layers according to temperature variations such as -
a) Troposphere b) Stratosphere c) Mesosphere d) Thermosphere e) Exosphere f) Magnetosphere
a) Troposphere
The troposphere is the first and lowest layer of the atmosphere of the Earth and contains 75% of the total mass of the planetary atmosphere and is where most weather phenomena occur. It is the heaviest and densest air layer. This is the level at which we live.
Features:
1) Temperature : 15 ° C to (-) 55 ° C.
2) Both the pressure and the temperature of this layer decrease with increasing height.
3) The temperature decreases by about 6.5 ° C with every 1 km increase in altitude.
4) The sky looks blue because of the dust at this level.
5) The top of the troposphere is called Tropopause.
6) The temperature in the Tropopause is approximately (-) 55 ° C.
7) The height of the troposphere is 15-16 km at the Earth's equator and 5 - 6 km at the North and South Poles. The height of this region increases in summer and decreases in winter.
b) Stratosphere
The stratosphere is the second layer of the atmosphere that extends from the top of the troposphere to an altitude of about 50 km, i.e. from 18 km to 50 km, and is where the temperature increases with increasing altitude.
Features:
1) Temperature : -55 ° C to 0 ° C.
2) This layer does not contain dust and water vapor etc. This layer is free from several associated turbulence like clouds, rains thunderstorms, lightning, etc. That is why this layer is called the dynamically stable.
3) For this reason jet planes move easily at this level.
4) The upper limit of the stratosphere is called stratopause. The air temperature here is 0 ° C or 32 F.
5) The air pressure at this level is 1/1000 part of the air pressure at sea level.
The Ozone concentration is higher in the upper portion of the stratosphere, from approximately 25 to 50 kilometers above Earth. So this layer is called the ozonosphere.
This layer absorbs the sun's harmful ultraviolet (UV) rays. As a result, ultraviolet (UV) rays cannot reach the earth. Ultraviolet (UV) rays are very harmful to the living world. So the Ozone layer protects the earth from harmful ultraviolet rays. As the ultraviolet rays from the sun are absorbed in this layer, its temperature increases. The temperature of this layer is about 76 ° C.
c) Mesosphere
The air layer that extends from the top of the stratosphere to an altitude of about 80 km where the temperature of the air decreases with increasing altitude is called the mesosphere.
Features:
1) Temperature : 0 ° C to (-) 93 ° C.
2) As the altitude increases at this level both temperature and pressure decrease and the minimum value of temperature is (-) 93 ° C. This is the lowest temperature in the atmosphere.
3) Small meteorites coming from space are burnt to ashes here.
4) The upper limit of the mesosphere is called mesopause.
d) Thermosphere or ionosphere
The region above the mesosphere is called Thermosphere or ionosphere (from 80 km to 500 km) Here the temperature rises rapidly as the altitude increases.
Features:
1) Temperature: from (-) 93 ° C to about 1200 ° C.
2) The ionosphere absorbs X-rays and gamma rays from the sun so the temperature of this layer is very high. The average temperature of this layer is about 1200 C.
3) The portion of the thermosphere where the air is ionized under the influence of cosmic rays, is called the ionosphere.
4) The ionosphere located at this level makes wireless communication possible on Earth.
5) Polar region where there is a night for 6 consecutive months, polar light or aurora is seen in the ionosphere of that region.
6) The orbit of the International Space Station (ISS) is located at this level.
7) There is almost no air here so the sky looks black.
e) Exosphere
There is an air layer that extends from the top of the thermosphere to an altitude of about 1600 km, i.e from 500 km to 1600 km above the surface, where the density of air is very low, it is called the exosphere.
Features:
1) Temperature: 1200 ° C to 1600 ° C.
2) Artificial satellites, space stations are located at this level.
3) The connecting layer of the thermosphere and exosphere is thermopause.
f) Magnetosphere
The layer that extends from the top of the exosphere to the end of the atmosphere (10000 km) is called the magnetosphere.
Temperature: more than 1600 C.
Variation of temperature and pressure depending on the height
The temperature decreases by about 6.5 ° C as the altitude increases per kilometer from the surface to about 50 km.
The force exerted by the wind perpendicularly on a single area around a point on the surface of the earth is called atmospheric pressure at that point.
Atmospheric pressure is measured using a barometer.
The higher you go above the surface, the lower is the air pressure. Generally, with every 1 km rise in height, the air pressure decreases by 8.5 cm.
Ozone layer formation and depletion
The upper part of the stratosphere contains the ozone layer. About 90% of the ozone gas in the atmosphere is stored at this level.
Formation of Ozone layer:
Ultraviolet (UV) rays emitted from the sun splits the oxygen molecule into individual oxygen atoms.
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| Oxygen molecules dissociate under the influence of ultraviolet rays |
The oxygen atoms produced in this way combine with an oxygen molecule to produce the ozone molecule (O3).
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| Formation of ozone molecules by combining with oxygen atoms and oxygen molecules |
Causes of Ozone Depletion
British scientist Joe Foreman (1982) first noticed that the Ozone layer in the stratosphere over Antarctica was getting thinner and thinner. This phenomenon is called depletion of the Ozone layer.
Destruction of the Ozone layer :
1) The role of CFC compounds:
Under the influence of ultraviolet rays, CFC gets dissociated and produces active chlorine atoms.
Under the influence of ultraviolet rays, CFC is dissociated, producing the active chlorine atom that converts ozone into oxygen.
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| Ozone molecule decomposition by CFC |
This process continues uninterrupted. An active chlorine atom is capable of decomposing one lakh ozone molecules.
2) The role of nitrogen oxides:
Due to the low density of air in the stratosphere, jet planes travel through this layer with relatively little obstruction. They emit large amounts of nitric oxide, which depletes ozone.
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The role of nitrogen oxides in the destruction of weight levels |
Harmful effects of ozone depletion:
a) Impact on humans:
1) Can cause skin cancer.
2) Ultraviolet rays can cause mutations in the human body's DNA
3) The skin turns tan or burns
4) Decreases fertility and immunity
5) Cataracts appear in the eyes and vision is reduced.
B) Effects on plants:
1) The photosynthesis process will be disrupted resulting in reduced grain production
2) The leaves will fade
3) Seed germination process will be disrupted.
c) Effects on the atmosphere:
Destruction of marine plankton and plankton-eating animals may occur.
d) Impact on climate:
1) If UV rays are directly exposed to the earth's surface, the surface temperature will increase and the melting of ice in the polar regions will increase the sea level.
2) The water in the reservoir will evaporate rapidly and climate change will occur.
3) The amount of acid rain will increase.
Greenhouse Effects and Global Warming
What is a greenhouse?
A greenhouse is a special type of house with a glass wall and a roof inside which vegetables and fruits are grown at low temperatures in winter countries. During the day, small wavelengths of light from the sun easily penetrate the glass and enter the room, and get reflected by the vegetables and tree saplings. That reflected rays with long wavelengths cannot penetrate the glass again and come out. so it is always warm inside the room.
Greenhouse effect
Gases such as carbon dioxide (CO2), water vapor (H2O), methane (CH4), CFC, etc. present in the Earth's atmosphere act as greenhouse gases. These gases allow short-wavelength rays from the sun to pass through and reach the Earth's surface. But prevent long-wavelength infrared (IR) rays radiated by the earth from returning into space. The net result is the warming up of the earth's atmosphere. This phenomenon is called the greenhouse effect and those gases are called greenhouse gases
Greenhouse gases
1) Carbon dioxide (CO2) 2) Methane (CH4) 3) Chlorofluorocarbon (CFC) 4) Ozone (O3) 5) Nitrous oxide (N2O) 6) Water vapor (H2O) etc.
*Oxygen (O2) and nitrogen (N2) in the atmosphere are not greenhouse gases.
Organic Greenhouse Gas: Methane (CH4)
The contribution of carbon dioxide (CO2), methane (CH4), chlorofluorocarbon (CFC), ozone (O3), nitrous oxide (N2O), and water vapor (H2O) to the greenhouse effect is respectively 50%, 19%, 16%, 8 %, 5%, and 2%.
The greenhouse effect of methane (CH4), nitrous oxide (N2O), and CFC is 25,250 and 20,000 times higher than that of carbon dioxide (CO2), respectively.
Global Warming: Global warming is the process of increasing the amount of greenhouse gases in the atmosphere and increasing the greenhouse effect.
As a result of global warming, the average temperature of the earth is increasing by about 0.05 ° C every year.
Potential effects of global warming:
1) Change of seawater:
A lot of ice in the polar region will melt, this will increase the sea level and flooding low-lying regions.
2) Climate change: There will be severe floods, droughts, storms, etc.
3) Public health: Climate change will affect public health. As the world warms, the incidence of various mosquito-borne diseases is likely to increase.
4) Unable to withstand high temperatures, many insects and birds will become extinct forever, damaging the ecosystem.
5) By the middle of this century, global warming will increase by about 2-4 ° C and will bring extreme natural disasters.
Effective ways to reduce greenhouse gas emissions
1) The use of fossil fuels should be gradually reduced and the use of alternative energy and renewable energy should be increased.
2) The use of vehicles powered by fossil fuels should be reduced instead, we should use solar-powered vehicles.
3) Plans need to be made to create more new forests without destroying them.
4) Stop production and use of CFC gas.
5) Convert various organic waste materials into organic fertilizers and use them.
6) Population needs to be controlled and people need to be made aware of the effects of global warming.
The usefulness of the greenhouse effect :
Without greenhouse gases, the reflected radiation from the earth would go back into space. As a result, the earth would become so cold that it would not be possible for any living thing to survive. Organisms exist on Earth because of the greenhouse effect.
Proper use of energy
We can roughly divide the energy source into two parts-
1) Non-Renewableor or conventional energy source
Such as fossil fuels, coal, petroleum, natural gas, etc
2) Renewable or unconventional energy
Such as solar energy, wind energy, water energy, tidal energy, geothermal energy, biomass energy, etc.
Fossil fuels
Fossil fuels are fuels produced from the remains of plants and animals.
Origin of fossil fuels
As a result of natural disasters, plants and animals are buried under the ground. Fossil fuels are formed due to the action of pressure, heat, and bacterial degradation of dead plants and animals buried under the earth's surface for millions of years.
The calorific value of fuel
The amount of heat energy produced by the complete combustion by a unit mass or volume of a fuel is called the calorific value of that fuel.
Its unit is calorie/gram (cal/g) or kilocalorie/cubic meter (kcal/m3) or kilojoules/kg (kJ / kg).
Here is the order of calorific value of some fuels
Wood < Coal < Petrol ~ Diesel ~ Kerosene > LPG < Liquid Hydrogen (H2).
The necessity of conservation of fossil fuels
1) Fossil fuel reserves are limited and it is not renewable.
2) Extensive use of fossil fuels will deplete its reserves at some point, resulting in an energy crisis.
3) Greenhouse gases produced using fossil fuels cause global warming.
4) We must save some amount of fossil fuels for future generations so that they can find time to find renewable energy sources using advanced technology.
The concept of sustainable development
Sustainable development is the development when natural resources are extracted and used in a well-controlled way for the development of the human race without completely depleting the natural resources for the sake of future generations.
Non-conventional source of energy:
Non-conventional sources of energy also known as Renewable sources of energy are those energies which can never be depleted.
Features of renewable energy
These energy sources are 1) readily available 2) less likely to be depleted 3) can be used repeatedly 4) does not cause environmental pollution.
Non-conventional energy sources:
1) Solar energy 2) Wind energy 3) Tidal energy 4) Geothermal energy 5) Biomass energy 6) hydropower etc.
Solar cells and their uses
A solar cell, or photovoltaic cell, is an electrical device that can convert Solar energy directly into electrical energy.
Generally impure Silicon or gallium semiconductors are used in solar cells.
Only 10% - 15% of the incident solar energy is converted into electrical energy. So a very small amount of electricity is generated in a solar cell (about 0.5 V).To increase efficiency, a large number of solar cells are placed side by side on a large surface. This system is called a solar panel or solar module.
Use of solar cells:
1) In artificial satellites power is supplied with the help of solar cells.
2) Solar cells can be used to generate electricity at a low cost without pollution.
3) Solar cells are used to run clocks, calculators, traffic signals, toys, etc.
4) Electricity generated from solar energy is used for cooking, running small pumps, radio-television, etc.
Biomass energy: Biomass is the organic matter excreted by the dead parts of plants and animals. The energy that we get from burning biogas directly is called biomass energy.
Its main component is methane gas. It also contains small amounts of CO2, H2, N2, CO, and water vapour.
Coalbed methane (CBM):
The methane gas that is absorbed in the solid layer of mineral coal is called Coal Bed Methane (CBM). It is a form of natural gas.
The methane gas that is collected in the coal seam in a coal mine before the coal is extracted is called Coal Bed Methane (CBM) or Coal Sim Gas (CSG).
It is also known as sweet gas because it does not contain toxic hydrogen sulfide (H2S) gas.
Components: Its main component is methane gas. It also contains small amounts of ethane, propane, butane, nitrogen, and carbon dioxide.
Methane Hydrate
Methane Hydrate: Methane hydrate is a cage-like structure formed by water molecules and Methane at low temperatures and high pressures.
The concentration of methane in it is very high so it generates a lot of heat when it burns, which is why methane hydrate is called fire ice. It is also called hydromethane, methane clathrate, methane ice, etc.
The symbol of methane hydrate is 4CH4,23H2O.
About 160 - 170 liters of methane gas is emitted from 1 liter of solid methane hydrate in STP.
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